The tax agency handed Republicans what could be a bombshell late on Friday, telling congressional investigators that a computer crash led to the loss of two years worth of emails from the figure at the center of the scandal: Ex-tax exempt IRS chief Lois Lerner, who the GOP accuses of using her position to go after the likes of Crossroads GPS and other conservative groups.

For the IRS, it is another unforced error for an agency that can ill afford one at the moment, elevating what was a waning controversy into what could be a years-old saga along the lines of Republicans persistence on Benghazi and the Fast and Furious matter.

House Ways and Means committee chairman Dave Camp (R-Mich) called for a special investigator to probe the matter on Monday, and said that IRS commissioner John Koskinen has agreed to testify before his panel on June 24 about what rules may have been broken and what steps the agency has made to recover the documents.

“The bottom line is we are going to find out what happened with this and we are not going to let up – we sent a letter to the President expecting his full cooperation in getting this matter resolved,” Charles Boustany (R-La.), who heads a subcommittee on Ways and Means, told POLITICO.

House Oversight chairman Darrell Issa (R-Calif.) also subpoenaed Koskinen to testify before his committee late on Monday.

And at least one top Democrat wants to know more. Senate Finance Chairman Ron Wyden (D-Ore.) called an emergency meeting on Monday evening with IRS Commissioner Koskinen to learn more about the news, a Finance source told POLITICO.

After the meeting Wyden merely said “I don’t have a comment right now.”

Koskinen after the Senate Finance meeting said that they found out about Lerner’s missing emails “late in the spring.”

“there’s no indication at all that anybody was trying not to keep the emails,” from investigators and said IRS officials “worked for several weeks trying to restore the emails in 2011.”

“They were unsuccessful, so it doesn’t appear from all the information that anybody was doing anything other than trying to retrieve the emails,” he said.

At the very least, the news opens up a whole new can of worms in the controversy — just as several congressional investigators were wrapping up their probes of the scandal.

Already, Republicans on the Senate Finance Committee — which, sources say, had pretty much wrapped up its bipartisan probe of the matter — are saying they’ll have dig in again to rework the case.

But even some somewhat more neutral observers say the email issue could be a game changer.

Chris Bergin, publisher at the nonprofit Tax Analysts, said in an interview that he always defended the IRS because he thought they just did something “really stupid” when they singled out conservative groups.

But the news over the weekend has changed his entire perspective of the controversy, he said.

“These developments are disturbing. … How do you lose email? Somebody received it right? This is worrisome… and it takes a year for them to tell us?” Bergin said.

The IRS says Lerner’s computer crashed in 2011, deleting her archived emails. Agency policy at the time did not require it to back up all employees’ emails. The IRS has been able to recover about 24,000 pieces of Lerner-related correspondence between January 2009 and April 2011 by searching the emails of other IRS employees where Lerner was on the email chains, according to the agency.

The Obama Administration said it can all be explained.

“You’ve never heard of a computer crashing before?” said Josh Earnest at a White House gaggle on Monday, disputing charges that the administration is hiding things, noting that the IRS has turned over 67,000 emails involving Lerner.

“If we’re trying to hide those letters and emails from Congressional oversight, there’s a pretty large loophole. … A good faith effort has been made,” Earnest said.

Meanwhile, the conservative blogosphere has been heating up since Friday.

“It’s pretty convenient that Lois Lerner’s emails also appear to be taking the fifth,” S.E. Cupp, a conservative host at CNN and Glenn Beck’s TheBlaze, said.

“Back when the press was still a reliable watchdog of the state, hard-nosed journalists would never have let this kind of corruption and cover-up sail through the political ether unscathed and unscrutinized. But with President Obama’s re-election secured, maybe there’s hope now that reporters put their politics aside and investigate these very serious charges.”

“That makes it look very suspicious, and put together with Lerner’s refusal to testify, even more so,” he said, later adding: “Now we find out that they’re only keeping their own documentation for six months? In the words of ESPN … come on, man.”

Senate Finance Republican staff aren’t happy because they were told they had all the documents related to the matter.

“It’s highly suspicious because we were told we had everything and now we don’t,” said one Republican panel source. “And now… a year after the fact, we’re being told this… Now, this without question delays the investigation.”

Defenders of Lerner point to emails they say show she tried in earnest to get her emails back.

“There were some documents in the files that are irreplaceable. Whatever you can do to help, is greatly appreciated,” Lerner wrote on July 19, 2011 in an email to someone helping her with her crashed computer.

That’s not likely going to appease conservatives that a conspiracy isn’t afoot, particularly because the time period for which the emails are missing is exactly when the IRS began singling out conservative groups.

Koskinen himself even admitted to POLITICO that there’s only so much the agency can retrieve on the Lerner emails: only emails she sent to other IRS staff, not emails she may have sent to other agencies.

“Any email in this gap period she sent outside [the agency] without a copy of anybody inside [the agency] we would not have,” he said.

That’s why some nonpartisan folks like Tax Analysts’ Bergin agree with Camp that it’s time for a special prosecutor: “It’s time the IRS and Treasury tell us what the heck went on here… If they don’t start leveling with the American people… there are other people who don’t like the IRS … who will start filling in the blanks.”